Regulation and phase equilibria of membrane lipids from Bacillus megaterium and Acholeplasma laidlawii strain A containing methyl-branched acyl chains.
Regulation and phase equilibria of membrane lipids from Bacillus megaterium and Acholeplasma laidlawii strain A containing methyl-branched acyl chains.
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含有甲基支链酰基链的巨大芽孢杆菌和莱氏无胆原体菌株 A 的膜脂的调节和相平衡。
作者：
L. Rilfors;Jon Hauksson;G. Lindblom
从20℃和55℃培养的巨芽孢杆菌（PE-20和PE-55）中分离出磷脂酰乙醇胺（PE）。异、反甲基支链饱和酰基链在巨藻中占主导地位，PE-55中异、反甲基支链的摩尔比值比PE-20高20倍以上。此外，PE-20的酰基链约有21摩尔%是单不饱和的。两种PE的相平衡存在差异：(1)PE-20比PE-55更容易形成反向的非层状相；(2) PE-20形成反立方相（I2）和反六方相（H(II)），而PE-55只形成HII相；(3) PE-20的层状液晶（L α）相比PE-55的L α相多吸收约70%的水。这些差异可以用酰基链组成的差异来解释。当生长温度升高时，为抵消温度对双分子层的不稳定作用，可能由巨芽孢杆菌合成非层状相倾向降低的PE分子。为了调节膜脂凝胶/结晶相和L - α相之间转变的温度，不需要调节酰基链组成。在37℃条件下，在15-(1,1,1(-2)H3)甲基十六烷酸、14-(1,1,1(-2)H3)甲基十六烷酸和13-(1,1,1(-2)H3)甲基十六烷酸培养基上培养菌株A-EF22，这些酸构成膜脂中84-89摩尔%的酰基链。当甲基分支从第15位移动到第13位时，两种主要脂质(单葡糖苷二酰基甘油（MGLcDAG）和二葡糖苷二酰基甘油（DGlcDAG）的摩尔比降低，阴离子脂质的摩尔分数增加。同时，在细胞和总脂质提取物中，甲基分支的顺序增加。在20 wt %的水条件下，研究了总脂提取物（去除中性脂）的相平衡，在63-67℃以上形成了HII和I2相。这些结果表明，极性头基组成的调节补偿了三种支链脂肪酸引入双分子层的酰基链填充的差异。脂质极性头基组成的调节不能调节脂质凝胶/结晶相和L - α相转变的温度，即向流体酰基链转变。（摘要删节为400字）
Phosphatidylethanolamine (PE) was isolated from Bacillus megaterium grown at 20 and 55 degrees C (PE-20 and PE-55). Iso and anteiso methyl-branched, saturated acyl chains are predominant in B. megaterium, and the value of the molar ratio of iso/anteiso acyl chains is more than 20-fold higher in PE-55 than in PE-20. Moreover, about 21 mol% of the acyl chains of PE-20 are monounsaturated. The phase equilibria differ between the two PE preparations: (1) PE-20 is more prone to form reversed nonlamellar phases than PE-55; (2) PE-20 forms both reversed cubic (I2) and reversed hexagonal (H(II)) phases while PE-55 forms only an HII phase; and (3) the lamellar liquid-crystalline (L alpha) phase of PE-20 takes up about 70% more water than the L alpha phase of PE-55. These differences can be explained by the differences in the acyl chain composition. When the growth temperature is raised, PE molecules with a reduced tendency to form nonlamellar phases are probably synthesized by B. megaterium in order to counteract the bilayer destabilizing effect of the temperature. The regulation of the acyl chain composition is not needed in order to regulate the temperature for the transition between gel/crystalline and L alpha phases of the membrane lipids. Acholeplasma laidlawii strain A-EF22 was grown at 37 degrees C on 15-(1,1,1(-2) H3)methylhexadecanoic acid, 14-(1,1,1(-2)H3)methylhexadecanoic acid or 13-(1,1,1(-2)H3)methylhexadecanoic acid, and these acids constituted 84-89 mol% of the acyl chains in the membrane lipids. The molar ratio between the two dominating lipids, monoglucosyldiacylglycerol (MGLcDAG) and diglucosyldiacylglycerol (DGlcDAG), decreased, and the molar fraction of the anionic lipids increased, when the methyl branch was moved from position 15 to position 13. Concomitantly, the order of the methyl branch increased in cells as well as in total lipid extracts. The phase equilibria of total lipid extracts (neutral lipids removed) were studied with 20 wt % of water, and HII and I2 phases were formed above 63-67 degrees C. These results indicate that the regulation of the polar head-group composition compensates for the difference in acyl chain packing introduced into the bilayer by the three branched-chain fatty acids. The regulation of the polar head-group composition of the A. laidlawii lipids cannot regulate the temperature for the transition between gel/crystalline and L alpha phases of the lipids, i.e. the transition to fluid acyl chains.(ABSTRACT TRUNCATED AT 400 WORDS)
水合二油酰磷脂酰乙醇胺膜中倒立立方相的观察。
影响因子：
2.9
作者：
Shyamsunder,E;Gruner,SM;Tate,MW;Turner,DC;So,PT;Tilcock,CP
通讯作者：
Tilcock,CP
含有支链磷脂的双层的热致性质。
影响因子：
2.9
作者：
Silvius,JR;Lyons,M;Yeagle,PL;O'Leary,TJ
通讯作者：
O'Leary,TJ
脂肪酰链长度和结构对磷脂酰乙醇胺水分散体的层状凝胶到液晶以及层状到反六方相变的影响。
影响因子：
2.9
作者：
Lewis,RN;Mannock,DA;McElhaney,RN;Turner,DC;Gruner,SM
通讯作者：
Gruner,SM